Showing papers on "Sine wave published in 1981"

Energy flow in the cochlea

Abstract: With moderate acoustic stimuli, measurements of basilar-membrane vibration (especially, those using a Mossbauer source attached to the membrane) demonstrate: a high degree of asymmetry, in that the response to a pure tone falls extremely sharply above the characteristic frequency, although much more gradually below it;a substantial phase-lag in that response, and one which increases monotonically up to the characteristic frequency;a response to a ‘click’ in the form of a delayed ‘ringing’ oscillation at the characteristic frequency, which persists for around 20 cycles. This paper uses energy-flow considerations to identify which features in a mathematical model of cochlear mechanics are necessary if it is to reproduce these experimental findings.The response (iii) demands a travelling-wave model which incorporates an only lightly damped resonance. Admittedly, waveguide systems including resonance are described in classical applied physics. However, a classical waveguide resonance reflects a travelling wave, thus converting it into a standing wave devoid of the substantial phase-lag (ii); and produces a low-frequency cutoff instead of the high-frequency cutoff (i).By contrast, another general type of travelling-wave system with resonance has become known more recently; initially, in a quite different context (physics of the atmosphere). This is described as critical-layer resonance, or else (because the resonance absorbs energy) critical-layer absorption. It yields a high-frequency cutoff; but, above all, it is characterized by the properties of the energy flow velocity. This falls to zero very steeply as the point of resonance is approached; so that wave energy flow is retarded drastically, giving any light damping which is present an unlimited time in which to dissipate that energy.Existing mathematical models of cochlear mechanics, whether using one-, two- or three-dimensional representations of cochlear geometry, are analysed from this standpoint. All are found to have been successful (if only light damping is incorporated, as (iii) requires) when and only when they incorporate critical-layer absorption. This resolves the paradox of why certain grossly unrealistic one-dimensional models can give a good prediction of cochlear response; it is because they incorporate the one essential feature of critical-layer absorption.At any point in a physical system, the high-frequency limit of energy flow velocity is the slope of the graph of frequency against wavenumberIn any travelling wave, the wavenumber is the rate of change of phase with distance; for example, it is 2π/λ in a sine wave of length λ. at that point. In the cochlea, this is a good approximation at frequencies above about 1 kHz; and, even at much lower frequencies, remains good for wavenumbers above about 0·2 mm−1 (which excludes only a relatively unimportant region near the base).Frequency of vibration at any point can vary with wavenumber either because stiffness or inertia varies with wavenumber. However, we find that models incorporating a wavenumber-dependent membrane stiffness must be abandoned because they fail to give critical-layer absorption; this is why their predictions (when realistically light damping is used) have been unsuccessful. Similarly, models neglecting the inertia of the cochlear partition must be rejected.One-dimensional modelling becomes physically unrealistic for wavenumbers above about 0.7 mni-1, and the error increases with wavenumber. The main trouble is that a one-dimensional theory makes the effective inertia ‘flatten out’ to its limiting value (inertia of the cochlear partition alone) too rapidly as wavenumber increases. Fortunately, a two-dimensional, or even a three-dimensional, model can readily be used to calculate a more realistic, and significantly more gradual, ‘flattening out’ of this inertia. All of the models give a fair representation of the experimental data, because they all predict critical-layer absorption. However, the more realistic two- or three-dimensional models must be preferred. These retard the wave energy flow still more, thus facilitating its absorption by even a very modest level of damping. The paper indicates many other features of these models.The analysis described above is preceded by a discussion of waves generated a t the oval window. They necessarily include: the already-mentioned travelling wave, or ‘slow wave’, in which the speed of energy flow falls from around 100 m s−l at the base to zero at the position of resonance;a pure sound wave, or ‘fast wave’, travelling a t 1400 m s-1, with reflection at the apex which makes i t into a standing wave. Half of the rate of working of the stapes footplate against the oval window is communicated as an energy flow a t this much higher speed down the scala vestibuli, across the cochlear partition and back up the scala tympani to the round window, whence it becomes part of the slow general apical progress of the travelling wave; a progress which, as described above, comes to a halt altogether just in front of the position of resonance.Mathematical detail is avoided in the discussion of cochlear energy flow in the main part of the paper (§ 1–10), but a variety of relevant mathematical analysis is given in appendices A–E. These include, also, new comments about the functions of the tunnel of Corti (appendix A) and the helicotrema (appendix C).

Fractional order sinusoidal oscillators: Optimization and their use in highly linear FM modulation

Abstract: After recalling the major disadvantages of integer order sinusoidal oscillators, we use noninteger order filters to make oscillators of fractional order greater than 2. These oscillators are unusual not only in their order but also in their properties, due to an uncommon form of the oscillator frequency as regards the direct production of low frequency sine waves. An algebraic performance criterion for the quality of systems just above the threshold of oscillation gives the optimum fractional order ensuring the sharpest tuning and the greatest frequency stability. The fact that the special form of the oscillation frequency in such systems satisfies the requirements of linearization of frequency modulation characteristics, is used in low frequency FM at large deviation and high linearity.

Practically perfect pitch

Abstract: People who can identify piano notes with essentially no errors (perfect pitch) are much less capable in identifying musical notes produced by sine waves. Thus, frequency is not the only information these people use to identify musical notes; piano notes are complex waveforms or patterns, sine waves are not complex. Musically trained people who do not have perfect pitch ability have considerable difficulty identifying either sine waves or piano notes. As well as this quantitative difference, these two groups of musicians also differ qualitatively. The people in both groups are about equally able to judge octave levels, but people with perfect pitch are excellent in identifying the particular note, e.g., E, independent of its octave, while people without perfect pitch ability are not.

Inverter for interfacing advanced energy sources to a utility grid

Abstract: A transistor is operated in the PWM mode such that a hlaf sine wave of current is delivered first to one-half of a distribution transformer and then the other as determined by steering thyristors operated at the fundamental sinusoidal frequency Power to the transistor is supplied by a dc source such as a solar array and the power is converted such that a sinusoidal current is injected into a utility at near unity power factor

Pitch for nonsimultaneous successive harmonics in quiet and noise

Abstract: Pitch perception was studied with respect to nonsimultaneous successive harmonics of fundamentals in quiet and noise. Stimuli consisted of three nonoverlapping sine waves each of 40‐msec duration. Pitch perception, examined by discrimination and matching, was found to correspond to spectral frequency in quiet and fundamental frequency in noise. The results suggest a pitch processor that integrates over time (synthetic mode) in noise and analyzes spectral components (analytic mode) in quiet. The findings are discussed with respect to current theories of pitch perception and auditory integrative functions. The findings are thought to be particularly relevant to analytic and synthetic modes of pitch perception.

Fault detection system as for locating faulty connections in a cable television system

Abstract: A fault detection system is provided for detecting and locating faulty connections in a cable TV system. First and second signals are generated at the head end transmitter. The first signal is a continuous wave signal. The second signal is a pulse modulated sine wave signal. A fault is indicated by the reception of a beat frequency signal between the first and second signals generated at the location of the faulty connection and returned to the head end. The location of the fault is determined by measuring the time interval between the transmission of the first and second signal and the return of the beat frequency signal, and relating such time interval measurement to the corresponding distance between the head end and the faulty connection.

Polyphase motor drive system with balanced modulation

Abstract: Sinusoidal excitation currents are supplied to the three terminals of a "wye" or "delta" connected three phase motor by an improved multiphase motor energizing drive system. For each terminal associated with a different phase, an individual feedback signal representing the current flowing into that respective terminal is sensed and subtracted from its corresponding controllable sine wave reference command to produce a current error signal for each terminal. The error signal for each of these currents is preferably converted to a two-state signal by means of an associated pulse width modulator. The modulator outputs are used to control power semiconductor switches which connect the corresponding motor terminal to either the positive or negative dc voltage. In the preferred system, for one of the terminals, the associated current feedback loop and reference command are omitted, and the associated pulse width modulator is driven by the inverted sum of the error signals from the other two phases. The result is inherently balanced multiphase excitation currents into the motor terminals.

Simulated space helmet

Abstract: A helmet having a built-in modulator and amplifier for voice alteration and projection is disclosed. The helmet includes a forwardly projecting nose housing having a viewing shield and an array of light emitting diodes. The light emitting diodes are coupled to the amplifier through a driver in which selected groups of the diodes are illuminated according to the intensity of the audio signal delivered by the amplifier. A loud speaker is mounted within the nose housing and is enclosed by a sidewall baffle. A microphone is mounted on the outside of the baffle and is connected to an audio alteration unit within the enclosure which includes an analog multiplier, a sine wave oscillator and an audio amplifier. The multiplier has an audio output corresponding to the product of the voice signal produced by the microphone and the sine wave oscillator signal. This produces a modulation effect which simulates an alien sound.

No-break power supply

Abstract: An A.C. power supply conditioner uses semi-conductor diodes (D1) and (D2) and energy storage capacitors (C1) and (C2) to produce a high D.C. voltage which is inverted at (TR1) and (TR2) to provide an A.C. output (L0, N0) without use of isolating transformer. A standby battery system includes a low voltage battery 'B' a DC/AC/DC converter 'E', and a charger 'F'. The inverter may provide a high frequency square wave, pulse-width modulated to form an effective sine wave at input frequency. In the event of a fault, switch G may be automatically changed-over.

Characterization of spatial and temporal properties of monkey LGN Y-cells

Abstract: LGN Y-cells in 3 anaesthetized (N2O/O2) and paralyzed rhesus monkeys were investigated with stimuli, intensity modulated by gaussian white noise, and with moving and counterphase modulated spatial sine wave gratings. The results support the model, postulated on the base of electrophysiological recordings in the retina of cat and mudpuppy, which consists of a linear centre and surround mechanism whose responses are modified in a frequency-selective multiplicative way by a nonlinear mechanism in the receptive field. This nonlinear mechanism is also held responsible for the second-order harmonic responses, which are the defining characteristic of Y-cells. The temporal and spatial characteristics of these mechanisms were determined. The responses obtained with the GWN stimulation and with modulated spatial sine wave gratings both indicate that the optimal temporal frequency of the linear mechanisms is near 7 Hz at 70 td and near 5 Hz for the nonlinear mechanism. The optimal spatial frequency for the linear mechanism is between 0.5---2 cycles/deg and between 6---12 cycles/deg for the nonlinear mechanism.

Raggedness of edges

Abstract: A series of psychophysical experiments was conducted to investigate the perception of raggedness of edge images whose tangential edge or boundary profiles are not straight. The profiles used were either sinusoidal or determined by the sum of several sine waves. In the first experiments the just-detectable or threshold amplitude of the sine wave was determined as a function of the sine-wave frequency. The observers’ sensitivities were maximum in the region of 1–2 cycles/mm at a viewing distance of 400 mm, at which the peak-to-peak threshold amplitude was approximately 7 μm; the threshold values increased at higher and lower frequencies. Experiments using the sum of two sine waves with a frequency ratio of 3:1 indicated that the detection threshold was not affected by the relative phase of the two components even though the shape and peak-to-peak amplitudes of the profiles changed radically. In a second set of experiments observers were asked to rate the raggedness of suprathreshold profiles relative to two anchor images. For sine-wave profiles raggedness ratings increased linearly with peak-to-peak amplitude. For two-component sine-wave profiles with a frequency ratio of 3:1, the rated raggedness was not affected by the relative phase of the components. The implications for a general model of raggedness perception and for a further understanding of spatial frequency channels in the visual system are discussed.

Signal processing system

Abstract: A signal processing system and technique is disclosed for detecting the pence of a desired frequency signal particularly that of a sine wave, in a noisy environment. The signal mixed with noise is received and analyzed by a Fast Fourier Transform spectrum analyzer the output of which is indicative of instantaneous signal phase. The output of the spectrum analyzer is digitally processed to produce a series of average instantaneous signal values based upon the instantaneous signal phase and a statistical estimate of its rate of change, the values being representative of the relative signal strengths for a progression of phase reference values between 0° and 360°. The desired signal is detected when an average instantaneous signal value exceeds a threshold value determined empirically based upon a certain probability of detection and false alarm rate.

Energy conservation system using current control

Abstract: An electrical energy conservation control method and apparatus are provided which produce efficient control of the light output of either incandescent or fluorescent lamps or the outputs of other electrical load devices under circumstances where the rated output is not required. The control method and apparatus combines electronic (transistor) switching techniques with the use of reactive circuit components to provide control of the magnitude of current flowing through the load device during the AC input voltage sine wave and to permit some current flow at all times during each voltage half wave. The control technique is non-dissipative in the sense that losses are virtually limited to switching transitions and passive circuit element losses. The control is accomplished by controlling the time period that a transistor is saturated full-on. The transistor is saturated on at the beginning of each voltage half wave and continues to be saturated on until the point in time within each half wave when the transistor is turned off. At that point in time, a non-dissipative current-limiting capacitor provides an alternate current path for the load current. This operation combats the intrinsic non-linear characteristics of inductive loads and causes less power factor change.

On detecting reflections in presence of scattering from amplitude statistics with application to D region partial reflections

Abstract: In many radar experiments which use transmission or scattering of radio waves through a random medium, the received signal is modeled as a reflected sine wave of amplitude A in a scattered narrow-band Gaussian random process of variance 2σ2. In this model the received signal amplitude has a Rice family of distribution characterized by a parameter α = A/σ. It is shown that amplitude statistics cannot be used to discriminate weak reflections from scattering (α < 0.5). Behavior of mean, skewness, and kurtosis of the normalized signal amplitude is examined for a constant and an intermittent reflected component. It is shown that intermittency has a strong effect on these. Applications to a D region partial-reflection experiment at Tromso are briefly discussed. It is shown that, at least in some simple cases, enhanced reflections arise from the top and bottom parts of turbulent layers.

Frequency shift keying system

Abstract: In a frequency shift keying system, sine waves of different frequencies f0 and f1 are selectively provided as a modulated output signal in accordance with the level of an input code. One of two pulse signals having frequencies N times higher than the frequencies f0 and f1 is selected by a selector in accordance with the level of the input code, and the selector output pulse signal is frequency divided by a counter down to 1/N to obtain a pulse signal having a duty ratio of 50% and a frequency of f0 or f1. The pulse signal obtained is converted by a low-pass filter into a sine wave. The modulated output signal has no phase shift even at the point of transition of the input code level and has continuity and hence has little modulation distortion.

Radio acoustic measurement of fog-capping thermal inversions

Abstract: The radio acoustic sounding system (RASS) is a remote technique for measuring temperature profiles in the lower troposphere1,2 In essence, it consists of a powerful acoustic source beaming a short burst of sinusoidal waves towards the zenith The speed of this pulse in its upwards path is proportional at every height to the square root of the local temperature This speed is continuously measured from the ground by means of a Doppler radar The radar echo is due to the change in refractive index of air compressed by the acoustic wave The faint echo is enhanced by choosing an acoustic wave in Bragg resonance with the radio wave The record of the measured sound speed displayed as a function of delay from the start of the acoustic beam leads to the acquisition of the temperature vertical profile We now describe the use of such a system at metre-wavelengths in the study of fog-capping thermal inversions at a site in the Po Valley

High voltage power supply

Abstract: A modified double Greinacher high voltage power supply wherein the side-string capacitances thereof have an inductance associated in series therewith, the inductance/capacitance circuits being appropriately tuned to the frequency of the R-F input voltage source. Preferably the center-string capacitance may have an inductance associated in series therewith, such circuit being similarly tuned. The input R-F voltage, rather than being supplied as a sine wave is supplied substantially as a square wave to the first stage and is transmitted to each of the subsequent stages substantially as a square wave.

Wideband linear carrier current amplifier

Abstract: An amplifier suitable for carrier current line driver applications is shown. It includes a triangle wave to sine wave shaper circuit and an automatic level control. It incorporates a line surge arrestor circuit that is active even when the transmitting capability is disabled. The circuit is shown in an integrated circuit form, the output of which is capable of being boosted by off-chip components.

Digital sine wave synthesizing method and apparatus

Abstract: A simple method and apparatus for generating approximate sine waves is described. A digital accumulator or adder is driven at a basic counting rate to accumulate increments representative of phase with the total sum representative of total phase angle of a sine wave. The output is periodically sampled and the value is converted into an analog output voltage in a normal D to A converter. A straight line ramp voltage approximation to the sine wave function is created as the result. The accumulator operates in this fashion until a total phase angle of approximately 45° is accumulated. Then accumulation value additions are then accorded 1/2 their usual significance until 671/2° of total phase angle are accumulated. Then accumulation is then at 1/4 the basic significance accorded to increments until 90° is reached. The symmetry of the sine wave allows the 0° through 90° samples to be used to generate the full 360° wave form by simple inversion or reverse counting of the counter and inversion of the algebraic sign as necessary. A binary slope approximation to the sine function is achieved by this technique. A series of straight line slopes with a slope of 1, 1/2 and 1/4 are utilized to approximately track a true sine function. The breaks in slope occur in a binarily related fashion to a 90° quarter cycle at 90°/2 and at 90°/4. These simple binary relationships allow the sine function to be approximated very easily by discrete logic and simple binary counters or parallel adders or by the equivalent counting in registers of a microprocessor. The resulting output is applied to a D to A converter to derive the output analog voltages.

Synthetic-Aperture Radar Based on Nonsinusoidal Functions: IX -Array Beam Forming

Abstract: For sinusoidal waves with bandwidth zero, one obtains the classical formula ϵ = κNL = kc//spl conint/L for the resolution angle of a sensor array, where L is the length of the array, λ the wavelength, /spl conint/the frequency, and c the phase velocity of the wave, while κis a constant whose value is usually chosen to be 1. Waves with the time variation of a rectangular pulse of duration ▵T yield the resolution angle ϵ = 2Kc/▵/spl conint/ P/P /sub N/, where P/P/sub N/ is the signal-to-noise ratio and ▵/spl conint/ = 1/2▵T the nominal bandwidth of the pulse; the same result holds for coded pulse sequences, such as Barker codes or complementary codes, if the main lobe of their auto-correlation function has the shape of a triangle with rise time ▵T. Hence, the resolution angle e can be reduced by increasing the signal power, as well as by increasing the array length L or the bandwidth ▵f. For sinusoidal waves, an increase of the signal power brings no reduction of the resolution angle. The trade between signal power and frequency bandwidth is of interest whenever the attenuation increases rapidly with frequency, e.g., in high-resolution all-weather radar or in underwater acoustic beam forming.

Calculation of square wave test for frequency optimised hot-film anemometers

Abstract: The response of a frequency optimised constant-temperature hot-film anemometer to an electronic step function is calculated using Laplace transform methods. It can serve as a standard of comparison during frequency optimisation of the anemometer by means of the convenient square wave test method.

Numerical control servo drive circuit

Abstract: of the Disclosure The resolver drive circuit on a numerical control system includes a microprocessor system which monitors the phase and amplitude of the sinusoidal wave forms applied to the resolver. Any changes in amplitude or phase shift of the applied wave forms due to such factors as time and temperature are automatically corrected by the microprocessor system. A highly accurate resolver position feedback system is thus formed with a minimal number of temperature sensitive components and a minimal number of required manual adjustments to analog circuitry.

Video signal monitoring device and method

Abstract: A device and method for monitoring a video signal formed by a train of horizontal sync pulses including odd and even numbered sync pulses and intermittent color burst signal portions located between successive horizontal sync pulses including a circuit for generating a first continuous signal in phase with the color burst signal portions, a circuit for generating a second continuous signal in phase with the odd numbered horizontal sync pulses, a demodulator circuit for demodulating the first signal with the second signal to produce a third signal, and a display device for displaying a vertical line and the third signal as a sine wave with the phase of the sine wave with respect to the vertical line being representative of the color burst signal portion to horizontal sync pulse phasing of the video signal. The horizontal sync pulses and the color burst signal portions of a second video signal may additionally be displayed as a second vertical line and a second sine wave on the display device so that a second video signal in a video system may be compared with the aforementioned video signal.

The instantaneous frequency of a Gaussian signal: The one-dimensional density function

Abstract: The density function of the instantaneous frequency of a Gaussian signal is derived without a narrow-band assumption It is possible to express this density using two parameters of the Gaussian signal, viz, the mean frequency and the intensity of zero-crossings, or alternatively, the mean frequency and the bandwidth It is shown that the probability of negative instantaneous frequencies is nonzero for all bandwidths except the limiting case of a purely sinusoidal wave

DC/AC High Power Cell Structure Improves Sine Generator Performance

Abstract: A new generation of dc/ac sine generators, based on dc/dc, pulse-width modulation (PWM) storage converter structure operating with rectified sine wave control and associated with a controlled bridge, is described. The efficiency, harmonic distortion, and transien't behavior are better in dc/dc sine convertors than conventional dc/ac sine convertors. Continuous non-linear or linear methods previously described can be extended to design this structure.

Apparatus and method for removal of sinusoidal noise from a sampled signal

Abstract: An apparatus and method for removing signal frequency sinusoidal noise from an analog signal is disclosed. The filter apparatus utilizes A Programmable Gain Amplifier (PGA) as an input to a discrete sine wave generator to control the amplitude and phase of the discrete sine wave generator. The output of the latter, after being full live rectified, controls the gain of the PGA so that its output, when appropriately phase shifted, cancels sinusoidal noise from a sampled analog signal. The apparatus is particularly adapted to cancelling 60 cycle noise from electrocardiogram (ECG) signals. The filtering approach can be implemented on a programmed general purpose digital computer and the method steps for achieving filtering of single frequency noise from an analog signal are disclosed.

Human Sensitivity to High Frequency Sine Wave and Pulsed Light Stimulation as Measured by the Steady State Cortical Evoked Response

Abstract: : The steady state cortical evoked response shows enhanced amplitude to a visual stimulus which is flickered in the frequency range between 38 Hz and 66 Hz. In this study, amplitude was found to be greatest at one particular frequency of stimulation, with the magnitude of the response to the peak frequency as much as double the amplitude of the surrounding frequencies. While all subjects demonstrated this enhancement, the particular frequency at which it was found varied from subject to subject. The range of peak frequencies was found to be 50 Hz to 56 Hz for the subjects studied. Sine wave modulated light produced this effect, while stroboscopic stimuli in the same frequency range did not produce it as clearly. It is hypothesized that this narrowly tuned response may be related to a subject's performance, as well as to other physiological characteristics of the individual. Since this amplitude increase is narrowly tuned, it is suggested that the advantages and disadvantages of stimulating humans at their peak frequency should be determined. Possible uses of this phenomena for studying brain functioning and behavior are discussed.

Diffusion coefficient for ions in the presence of a coherent lower hybrid wave

Abstract: When the amplitude of a coherent lower hybrid wave exceeds a certain stochasticity threshold, the ion motion becomes ergodic. The problem of determining the resulting diffusion coefficient is considered. For large amplitude waves it is found that the diffusion coefficient oscillates with decreasing amplitude about the quasi‐linear value as the wave amplitude is increased. Furthermore, the diffusion coefficient is shown to be subject to narrow resonances at particular values of the wave amplitude.

Rotation speed detection device having a rotation angle detector of inductive type

Abstract: A detection head unit comprises a stator and a rotor. The stator has four poles disposed circumferentially at an interval of 90°. The poles have primary coils and secondary coils wound thereon. Two radially opposing poles constitute a pole pair. The primary coils wound on the poles constituting the pole pair are connected in series and in opposite phase with each other and one pole pair is excited by a sine wave signal and the other pole pair by a cosine wave signal. The rotor is of such a configuration, e.g. an eccentric rotor, as to change reluctance of the respective stator poles in accordance with a rotation angle and change reluctance in a differential manner between the two poles constituting the pole pair. An output signal resulting by phase shifting the sine wave signal applied to the primary coil in accordance with a rotation angle of the rotor is provided by a secondary coil. The rotation angle is detected by measuring phase difference between the reference signal and the output signal of the secondary coil. The rotation speed can be detected by detecting difference in frequency or period between the reference signal and the output signal. Further, acceleration in rotation can be detected by detecting an amount of change in the rotation speed. The detection device of a high resolution can be obtained by providing teeth of a certain pitch on the periphery of the rotor and teeth corresponding to the rotor teeth on the stator poles.